Research article
Large environmental disturbances caused by magmatic activity during the Late Devonian Hangenberg Crisis

https://doi.org/10.1016/j.gloplacha.2020.103155Get rights and content
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Highlights

  • The Hangenberg Black Shale (HBS) was deposited under anoxic to euxinic conditions in subtropical deepest water sites.

  • The onset of the Hangenberg Black Shale is characterized by negative carbon isotope excursion.

  • Anomaly mercury concentrations and Hg/TOC ratios were documented in the Carnic Alps and Thuringia.

  • The presence of pyroclastic material was confirmed before the deposition of the HBS.

  • Intensive magmatic activity was a trigger for climatic changes, excessive eutrophication, and deposition of the HBS.

Abstract

A wide range of various proxies (e.g., mineralogy, organic carbon, inorganic geochemistry, C and Mo isotopes, and framboidal pyrite) were applied for interpretation of changing oceanic redox conditions, bioproductivity, and the regional history of magmatic activity. This resulted in internally consistent interpretation of the late Famennian Hangenberg Crisis in subtropical deepest water sites of the epeiric Rhenohercynian and Saxo–Thuringian basins, as well as more open sites of the Paleo-Tethys Ocean.

High mercury concentrations were detected in all of the studied sections, with the highest values strata in the Carnic Alps (up to 20 ppm) and Thuringia (up to 1.5 ppm). The beginning of the Hg anomaly and the presence of pyroclastic material, indicate that local magmatic activity was initiated before the deposition of the Hangenberg Black Shale (HBS). The onset of the HBS deposition coincided with the expansion of phosphate-enriched, anoxic to euxinic waters during short-lived CO2-greenhouse spike of a warm–humid climate. Intensive magmatic activity was a trigger for climatic changes, an excessive eutrophication, and an accelerated burial of organic carbon during the Hangenberg transgressive pulse. The injection of catastrophic amounts of CO2, toxic elements and acids from volcanic activity could have led to acidification, mutation of spores, and episodes of mass mortality of marine plankton.

Keywords

Carbon and molybdenum isotopes
Volcanic activity
Inorganic geochemistry
Mineralogical composition
Redox conditions
Hangenberg Black Shale

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